Tow spreading device



March 11, 1969 0 w. APPEL 3,431,602

TOW SPREADING DEVICE Filed June 1, 1967 Sheetof 2 March 11, 1969 o. w. APPEL 3,431,602

TOW SPREADING DEVICE Filed June 1, 1967 Sheet 2 of2 J 4 d. 1' %M 24 Iii 40a.

7 Claims ABSTRACT OF THE DISCLOS A pneumatic spreader for spreading filamentary tow having an are shaped air discharge orifice discharging at an acute angle into a tow carrying passage for providing a fan shaped current of air traveling to the outlet end of the tow carrying passage.

The invention relates to the processing of textile filaments and more particularly to an apparatus and process for spreading filamentary tow to separate the filaments and provide a uniform distribution of the filaments in the tow. The term tow is used to mean a strand of yarn composed of a large number of continuous filaments, and a single tow usually consists of from 500 to 5,000,000 single filaments which range in size from a fraction of a denier to 30 denier per filament.

Continuous filament tow generally has a number of different kinds of imperfections arising during the processing of the tow. The individual filaments of tow are crimped to maintain the integrity of a band of the tow and to facilitate handling. This crimping gives rise to imperfections referred to shiners or married fibers which arise from the conjunction of a plurality of adjacent fibers and particularly the crimps in the tow band into a compacted mass, or wherein two or more filaments are so stuck together and do not easily separate in textile processing. Such shiners or married fibers, if not removed, cause a staple of poor openness having obvious disadvantages. Other imperfections arise for other reasons, such as due to the packaging of the tow in supply bales for implementing handling. When tow is removed from a supply bale, the tow band may have false twist, folds and undesired variations in width, and such irregularities detract from the desired appearance and strength of yarn produced from the tow.

In order to solve the problems due to these imperfections, a number of spreading techniques have evolved for separating the filaments comprising the tow and distributing them with relatively uniform spacing. Mechanical spreaders, such as of the type including pairs of rolls which are helically fluted on their peripheries, are one approach. However, such spreaders, particularly with relatively low denier fine filament tow, often tend to compress adjacent filaments so as to detract from the desired opening function. Pneumatic tow spreaders have also been proposed in which an air stream is directed against the tow serving to fluff up and separate the filaments comprising the tow. Such air spreaders may, for example, comprise a plurality of separate slots extending at acute angles with respect to the direction of movement of the tow over the slots and discharging normally to the surface in which the slots are cut and over which the tow passes. Such a spreader may also comprise a single straight slot extending at right angles to the direction of movement of the tow over the slot and also discharging normally to the surface in which the slot is cut and over which the tow passes. The type of air spreader having the acutely extending slots presents problems in that the air stream is not applied to the tow being processed with desired uniformity, and the other type of air spreader with the single transverse slot has been found to provide an inadequate spreading action for the tow. Also, both types of pneumatic tow spreaders tend to blow the tow apart as the tow passes over the slots.

It is accordingly a prime object of the present invention to provide an improved pneumatic tow spreader in which substantially all of the air discharged onto the tow is directed in the direction of movement of the tow so that the tow is not blown apart by the air and in which the air is discharged in an are so as to provide a tow spreading action due to the direction of movement of the air.

The invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above stated objects, and such other objects, as will be apparent from the following description of a preferred form of the invention, illustrated with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view of a pneumatic tow spreader incorporating the principles of the invention and partially cut away to show the internal construction of the tow spreader;

FIG. 2 is a sectional view taken on line 22 of FIG. 1;

FIG. 3 is a top plan view of the tow spreader with portions cut away to show internal construction; and

FIG. 4 is a sectional view similar to FIG. 2 and on an enlarged scale and showing a fragmentary portion of a central part of the flow spreader.

Like characters of reference designate like parts in the several views.

Referring now to the drawings, the illustrated tow spreader may be seen to comprise an air conduit 10 having side walls 11 and 12 and bottom and top walls 13 and 14. A bottom orifice plate 15 is fixed on the wall 14, and the wall 14 and plate 15 are provided with registering openings 16 and 17.

A top orifice plate 18 is disposed over and in parallel relationship with the plate 15 and is held in spaced relation with respect to the plate 15 by means of a separator plate 19 so as to thereby provide an air passage 20 between the plates 15 and 18. A top spreader plate 21 is provided above and in parallel relationship with the plate 18 and is held in spaced relation with respect to the plate 18 as by means of spacer plates 22 and 23 at the ends of the plates 18 and 2.1. A bottom spreader plate 24 is supported from and in parallel relationship with the top spreader plate 21 by means of spacer plates 25 and 26 located at the ends of the plates 21 and 2:4. The plates 22, 23, 25 and 26 are of the same thickness so as to provide a uniform thickness tow passage 27 between the plate 21 on the top and the plates 18 and 24 on the bottom.

The conduit 10 is straight, and the edges 15a, 18a and 21a of the plates 15, 18 and 21 are likewise straight and extend approximately above the side wall 11 of the conduit 10. The opposite edges 21b, 24b and 15b of the plates 21, 24 and 15 are are shaped; and the edges 21b and 24b are in substantial alignment while the edge 15b is disposed considerably short of the edges 21b and 241:.

An air orifice blade 28 is fixed on the edge 15b of the bottom plate 15. Although the blade 28 may originally be in fiat form, it also has the same arc shape as the edge 15b by virtue of being fixed on the arc shaped edge 15b. The blade 28 has a sharp upper edge 28a which is disposed in close proximity to the flat lower surface 18c of the bottom spreader plate 18 so as to form an are shaped orifice 29 at the end of the air passage 20.

An arc shaped slot 30 having a relatively narrow lower portion 30a and a relatively wide upper portion 30b is provided between the plates 18 and 24 and outside of and adjacent to the orifice 29. The slot 30 is defined by a downwardly facing surface 31 formed on the plate 18,

an upwardly facing surface 32 formed on the plate 24, and another upwardly facing surface 33 formed on the plate 18. The surfaces 31, 32 and 33 in cross section, as seen in FIG. 4 for example, are all flat; but it will be understood that these surfaces are arc shaped in plan. The surfaces 31 and 32 extend in the same general direction, away from the air orifice blade 28 and very generally in the directions A toward the arc shaped plate edges 21b and 24b, and the surfaces 3 1 and 32 are respectively disposed at acute angles a and b with respect to the lower fiat plate surfaces 180 and 240 which are in alignment in the illustrated embodiment. The surface 31 extends between the are shaped corners c and d; the surface 32 extends between the are shaped corners e and f; and the surface 33 extends between the are shaped corners d and g. Looking at the surfaces 31, 32 and 33 in cross section, as for example in FIG. 4, it will be observed that the are shaped surface 33 extends at an angle h, which is slightly less than a right angle, with respect to the arc shaped surface 31. The are shaped corner d thus is quite sharp. The are shaped surface 32 extends at an angle i with respect to the upper surface 24d of the plate 24, and the angle i is a relatively large obtuse angle so that the corner is relatively blunt. The complement of the angle i, namely the angle j, is that acute angle at which air discharges into the passage 27, as will appear from the following statement of operation of the tow spreader.

The tow passage 27 is of sufficient width so that tow 34, particularly a bundle of continuous synthetic filaments, may be drawn through the passage 27 as illustrated. The filaments may be drawn through the passage 27 by any suitable means such as, for example, by positively driven rolls (not shown). Air under pressure is supplied within the conduit 10, and the air passes upwardly through the openings 16 and 17 from the interior of the conduit and into the air passage 20. The air discharges through the arc shaped orifice 29 between the sharp upper edge 28a of the blade 28 and the lower fiat surface 180 of the plate 18 and enters the narrow portion 30a of the are shaped slot 30. Initially, the air travels principally on the arc shaped surface 31 due to the Coanda effect, which is the tendency of a thin fiow of fluid to follow the curvature of a boundary once it makes contact therewith. The air leaves the surface 31 at the end of the narrow slot portion 30a and leaves the corner d, which constitutes a sharp break, as a free jet and then transfers onto the are shaped surface 32. The air follows the surface 32 and around the blunt obtuse corner 1 into the passage 27, also due to the Coanda effect, traveling at this time in the directions A and on the upper surface 24d of the bottom spreader plate 24. The slot 30 is arc shaped, and thus the air flows between the plates 21 and 24 in radiating directions, as may be seen from FIG. 3-the arrows A are intended to indicate these directions which radiate in plan view but which are parallel to the adjacent surfaces of the top plate 21 and the lower plates 18 and 24 forming the passage 27, as seen in the sectional views.

The air discharging through the orifice 29 into the entrance end 30a of the slot 30 entrains additional air at the arc shaped corner c so that the air flows through the slot portion 30a is of greater volume than the volume of air discharged through the orifice 29. A secondary air flow is also picked up at the relatively wide exit end 30b of the slot 30 from the entrance end of the passage 27, and thus the flow of air in the directions A is of greater volume than the actual air flow through the slot 30, and the fiow of air through the passage 27 is from its entrance end to its exit end, namely, from left to right, as seen in FIGS. 1 and 2.

The filament spreading apparatus of the invention functions on the principle that a series of filaments in an air stream tend to become aligned with the How and they waiver or flutter in the flow and thereby become disentangled one from another, even though the filaments are crimped and even though the crimps are initially in register; and the filaments, by natural interference in the state of fluttering, become uniformly spaced on the average. Maximum advantage is taken of this natural effect of an air stream on filaments by having the slot 30, the orifice 29 and the edges 21b and 24b are shaped so that the air discharged into the passage 27 from the slot is in the shape of an arc and the air flows radially toward the exit end of the passage 27 in the directions A to thereby spread the filaments radially.

The apparatus of the invention is particularly elficient in spreading tow into a wide web of uniformly spaced filaments not only due to the use of a continuous radial jet of air from the arc shaped slot 30, but also due to the fact that the flow of air through the passage 27 through which the tow 34 passes is unidirectional, the flow of air being in the directions A from the tow inlet end to the tow outlet end of the passage 27. Such a unidirectional fiow of air may be contrasted with the flow of air in prior art spreaders which discharge air at right angles to the plane of the tow and in which approximately half of the air discharges counter to the direction of travel of the tow. This unidirectional air flow helps to convey the tow, to maintain a uniform tension in the filaments and to promote fluttering and consequent disentanglement and disengagement of the filaments with respect to each other, even though the filaments have been preliminarily crimped. Due to the fact that the orifice 29 is preferably relatively thin, the orifice 29 and the slot 30 provide a high velocity on the upper surface 24d of the bottom spreader plate 24, but this is of small volume for purposes of economy, and due to the high arr velocity, the air spreader is particularly efiicient in disentangling the filaments of the tow.

Although the air pressure in the conduit 10 may vary between relatively wide limits and may be as high as 15 p.s.i.g., one of the advantages of this type of tow spreader, which cntrains secondary air flow both at the entrance end of the slot 30 and also at the exit end of the slot 30, is that the required plenum pressure in the conduit 10 normally does not exceed 7 p.s.i.g. and may be as little as 3 p.s.i.g. in some cases. The angles a and b may well be between 15 and but preferably they are between 15 and 30. The angles a and b may be equal, or angle b may be greater than angle a to promote movement of air from the beveled surface 31 to the beveled surface 32. With respect to the orifice 29, the orifice is preferably very thin, and it may be as small as .005 inch in thickness, but it may well be as large as inch. The spacing between the beveled surfaces 31 and 32 may be as small as inch or as large as inch or more; but, in general, a small spacing is desirable to facilitate the transfer of the air flow from the beveled surface 31 to the beveled surface 32.

The gap between the surfaces 31 and 32 may be adjusted in order to control the amount of secondary air entering the entrance end 30a of the slot 30 and for adjusting the proximity of the air flow to the surface 32; and this adjustment may be made simply by slightly moving the bottom spreader plate 24 with respect to the top spreader plate 21. It should be noted that the are shaped surfaces 31, 32 and 33 are formed on the edges of the spreader plates 18 and 24, which are separate pieces, so that the surfaces 31, 32 and 33 may be formed very accurately, as by separately milling the edges of the two pieces 18 and 24, and the thickness of the slot 30 both between the surfaces 31 and 32 and also between the surfaces 33 and 32 may be uniform. This slot of very uniform thickness may be contrasted with a very thin slot milled into a single piece of material which tends to be quite non-uniform in thickness. With such a uniform thickness slot 30, the fiow of air through the slot 30 may be uniform from one end of the slot to the other end, and a uniform spreading action on the filaments of the tow is obtained due to this reason. It will be understood also that, if desired, the slot 30 may be made narrower or wider at various places. For example, if it is desired that the air flow be greater at the ends of the slot 30 to cause a greater filament spreading action to exist at the ends of the slot, the slot at its ends can be made wider than at its center.

Although the radius of the arc shaped slot 30 may vary within wide limits, the radius may, for example, well be from one foot to five feet; and, of course, as is obvious from the drawings, the center of the are shaped slot is located on the longitudinal center line of the tow carrying passage 27 and on the same side of the slot as is the entrance end of the tow carrying passage 27 which is shown on the left side in the FIG. 1 view, so that there is a sidewise spreading component of force on the tow as it passes from the inlet end of the passage 27 to the are shaped outlet end of the passage 27. The tow spreader of the invention is not limited insofar as width is concerned, but it has been found particularly effective to spread tow from an initial width of 12 inches to a final width of 24 inches, for example.

Since the flow of air from the slot 30 is radial and fan shaped and since the flow of air through the passage 27 is unidirectional, greater spreading and better uniformity in spreading tow into a wide sheet of essentially uniformly spaced individual strands can be assured than is possible with prior tow spreaders of the pneumatic type. In the event it is desired to obtain spreading in very large widths, several spreaders of the type described herein may be used in series or tandem. In between individual ones of such a series of spreaders, conventional mechanism may be used if desired for deregistering crimps in the filaments and thus assisting the tow spreaders of the invention in this respect.

I wish it to be understood that the invention is not to be limited to the specific constructions and arrangements shown and described, except only insofar as the claims may be so limited, as it will be understood to those skilled in the art that changes may be made without departing from the principles of the invention.

What is claimed is:

1. A tow spreading device having opposite faces defining between them a relatively thin wide passage which has an inlet end and an outlet end and through which filamentary tow may be drawn from the inlet end to the outlet end, one of said faces being provided with an elongate slot therein which has substantially parallel slot defining edges and which is in the shape of a curve having its center substantially on the longitudinal center line of said passage and more adjacent to said inlet passage end than to said outlet passage end for discharging a gas into said passage in a fan shape to thereby spread the tow as the tow travels from the inlet end to the outlet end of said passage.

2. A tow spreading device as set forth in claim 1 and also having a pair of opposite surfaces which terminate at said edges and which extend generally parallel to each other and at acute angles to said one face to form said slot along with said edges whereby gas from said slot flows toward the outlet end of said passage.

3. A tow spreading device having opposite faces defining between them a relatively thin wide passage which has two opposite sides and which has an inlet end and an outlet end whereby filamentary tow may be drawn through the passage from the inlet end to the outlet end, one of said faces being provided with an elongate slot therein which extends from substantially one side of said passage to the other side thereof and which is in the shape of a curve having its center more adjacent to said inlet passage end than to said outlet passage end for discharging a gas into said passage in a fan shape to thereby spread the tow as the tow travels from the inlet end of said passage to the outlet end thereof.

4. A tow spreading device comprising plate portions having opposite faces providing between them a relatively thin wide passage which has an inlet end and an outlet end and through which filamentary tow may be drawn from the inlet end to the outlet end, said plate portions on one of said faces being spaced from each other and having surfaces that extend in the same general direction so as to form an elongate slot which is in the shape of an are having its center substantially on the longitudinal center of said passage and on the same side of the slot as the inlet end of said passage and said surfaces extending at an acute angle to said one face and to said passage in the direction from said inlet end to said outlet end, and means for connecting said slot to a source of air under pressure so that air flows through said slot in the direction of movement of the tow and in a fan shape for thereby spreading the tow.

5. A tow spreading device as set forth in claim. 4, the one of said slot forming surfaces more adjacent to said inlet end than to said outlet end of said passage being cut back on said one face of said passage so as to provide a sharp corner in said slot whereby air tends to follow the other one of said slot forming surfaces which is more adjacent to the outlet end of said passage.

6. A tow spreading device comprising plate portions having opposite faces providing between them a relatively thin wide passage which has an inlet end and an outlet end and through which filamentary tow may be drawn from the inlet end to the outlet end, said plate portions of one of said faces being spaced from each other and having surfaces that extend in the same general direction so as to form an elongate air slot which is in the shape of an arc having its center on the same side of the slot as the inlet end of said passage, and means providing a thin air orifice located adjacent the air entrance end of said slot and the end of the one of said slot forming surfaces more adjacent the inlet end of said passage whereby air from the orifice tends to initially follow this slot forming surface.

7. A tow spreading device comprising plate portions having opposite faces providing between them a relatively thin wide passage which has an inlet end and an outlet end and through which filamentary tow may be drawn from the inlet end to the outlet end, said plate portions on one of said faces being spaced from each other to form an air slot between them which is in the shape of an are having its center on the same side of the slot as the inlet end of said passage and said slot extending generally at an acute angle to said passage in the direction from said inlet end to said outlet end, a plate member disposed along one of said plate portions defining said slot and providing an air supply passage between it and this plate portion and having an arc shaped edge, and an orifice blade fixed to said edge and extending toward said last mentioned plate portion so as to provide an are shaped orifice which generally coincides with the air inlet end of said slot and is at the side of the slot more adjacent the inlet end of said passage whereby air discharging through said orifice may pass through said slot and into said passage.

References Cited UNITED STATES PATENTS 3,231,165 1/1966 Wallin et a1. 22697 3,267,017 8/1966 Greene et al 226-97 XR 3,286,307 11/1966 Watson.

3,325,906 6/1967 Franke ,2267 XR 3,345,697 10/1967 Aspy.

FOREIGN PATENTS 921,229 3/1963 Great Britain.

MERVIN STEIN, Primary Examiner.

IRA C. WADDY, JR., Assistant Examiner.

U.S. Cl. X.R. 28-1; 226-97 

